Merge branches 'fixes' and 'devel-stable' into for-linus

[mirror_ubuntu-artful-kernel.git] / kernel / irq / manage.c

/*
 * linux/kernel/irq/manage.c
 *
 * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
 * Copyright (C) 2005-2006 Thomas Gleixner
 *
 * This file contains driver APIs to the irq subsystem.
 */

#include <linux/irq.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/sched.h>

#include "internals.h"

#ifdef CONFIG_IRQ_FORCED_THREADING
__read_mostly bool force_irqthreads;

static int __init setup_forced_irqthreads(char *arg)
{
        force_irqthreads = true;
        return 0;
}
early_param("threadirqs", setup_forced_irqthreads);
#endif

/**
 *      synchronize_irq - wait for pending IRQ handlers (on other CPUs)
 *      @irq: interrupt number to wait for
 *
 *      This function waits for any pending IRQ handlers for this interrupt
 *      to complete before returning. If you use this function while
 *      holding a resource the IRQ handler may need you will deadlock.
 *
 *      This function may be called - with care - from IRQ context.
 */
void synchronize_irq(unsigned int irq)
{
        struct irq_desc *desc = irq_to_desc(irq);
        unsigned int state;

        if (!desc)
                return;

        do {
                unsigned long flags;

                /*
                 * Wait until we're out of the critical section.  This might
                 * give the wrong answer due to the lack of memory barriers.
                 */
                while (desc->istate & IRQS_INPROGRESS)
                        cpu_relax();

                /* Ok, that indicated we're done: double-check carefully. */
                raw_spin_lock_irqsave(&desc->lock, flags);
                state = desc->istate;
                raw_spin_unlock_irqrestore(&desc->lock, flags);

                /* Oops, that failed? */
        } while (state & IRQS_INPROGRESS);

        /*
         * We made sure that no hardirq handler is running. Now verify
         * that no threaded handlers are active.
         */
        wait_event(desc->wait_for_threads, !atomic_read(&desc->threads_active));
}
EXPORT_SYMBOL(synchronize_irq);

#ifdef CONFIG_SMP
cpumask_var_t irq_default_affinity;

/**
 *      irq_can_set_affinity - Check if the affinity of a given irq can be set
 *      @irq:           Interrupt to check
 *
 */
int irq_can_set_affinity(unsigned int irq)
{
        struct irq_desc *desc = irq_to_desc(irq);

        if (!desc || !irqd_can_balance(&desc->irq_data) ||
            !desc->irq_data.chip || !desc->irq_data.chip->irq_set_affinity)
                return 0;

        return 1;
}

/**
 *      irq_set_thread_affinity - Notify irq threads to adjust affinity
 *      @desc:          irq descriptor which has affitnity changed
 *
 *      We just set IRQTF_AFFINITY and delegate the affinity setting
 *      to the interrupt thread itself. We can not call
 *      set_cpus_allowed_ptr() here as we hold desc->lock and this
 *      code can be called from hard interrupt context.
 */
void irq_set_thread_affinity(struct irq_desc *desc)
{
        struct irqaction *action = desc->action;

        while (action) {
                if (action->thread)
                        set_bit(IRQTF_AFFINITY, &action->thread_flags);
                action = action->next;
        }
}

#ifdef CONFIG_GENERIC_PENDING_IRQ
static inline bool irq_can_move_pcntxt(struct irq_desc *desc)
{
        return irq_settings_can_move_pcntxt(desc);
}
static inline bool irq_move_pending(struct irq_desc *desc)
{
        return irqd_is_setaffinity_pending(&desc->irq_data);
}
static inline void
irq_copy_pending(struct irq_desc *desc, const struct cpumask *mask)
{
        cpumask_copy(desc->pending_mask, mask);
}
static inline void
irq_get_pending(struct cpumask *mask, struct irq_desc *desc)
{
        cpumask_copy(mask, desc->pending_mask);
}
#else
static inline bool irq_can_move_pcntxt(struct irq_desc *desc) { return true; }
static inline bool irq_move_pending(struct irq_desc *desc) { return false; }
static inline void
irq_copy_pending(struct irq_desc *desc, const struct cpumask *mask) { }
static inline void
irq_get_pending(struct cpumask *mask, struct irq_desc *desc) { }
#endif

/**
 *      irq_set_affinity - Set the irq affinity of a given irq
 *      @irq:           Interrupt to set affinity
 *      @cpumask:       cpumask
 *
 */
int irq_set_affinity(unsigned int irq, const struct cpumask *mask)
{
        struct irq_desc *desc = irq_to_desc(irq);
        struct irq_chip *chip = desc->irq_data.chip;
        unsigned long flags;
        int ret = 0;

        if (!chip->irq_set_affinity)
                return -EINVAL;

        raw_spin_lock_irqsave(&desc->lock, flags);

        if (irq_can_move_pcntxt(desc)) {
                ret = chip->irq_set_affinity(&desc->irq_data, mask, false);
                switch (ret) {
                case IRQ_SET_MASK_OK:
                        cpumask_copy(desc->irq_data.affinity, mask);
                case IRQ_SET_MASK_OK_NOCOPY:
                        irq_set_thread_affinity(desc);
                        ret = 0;
                }
        } else {
                irqd_set_move_pending(&desc->irq_data);
                irq_copy_pending(desc, mask);
        }

        if (desc->affinity_notify) {
                kref_get(&desc->affinity_notify->kref);
                schedule_work(&desc->affinity_notify->work);
        }
        irq_compat_set_affinity(desc);
        irqd_set(&desc->irq_data, IRQD_AFFINITY_SET);
        raw_spin_unlock_irqrestore(&desc->lock, flags);
        return ret;
}

int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
{
        unsigned long flags;
        struct irq_desc *desc = irq_get_desc_lock(irq, &flags);

        if (!desc)
                return -EINVAL;
        desc->affinity_hint = m;
        irq_put_desc_unlock(desc, flags);
        return 0;
}
EXPORT_SYMBOL_GPL(irq_set_affinity_hint);

static void irq_affinity_notify(struct work_struct *work)
{
        struct irq_affinity_notify *notify =
                container_of(work, struct irq_affinity_notify, work);
        struct irq_desc *desc = irq_to_desc(notify->irq);
        cpumask_var_t cpumask;
        unsigned long flags;

        if (!desc || !alloc_cpumask_var(&cpumask, GFP_KERNEL))
                goto out;

        raw_spin_lock_irqsave(&desc->lock, flags);
        if (irq_move_pending(desc))
                irq_get_pending(cpumask, desc);
        else
                cpumask_copy(cpumask, desc->irq_data.affinity);
        raw_spin_unlock_irqrestore(&desc->lock, flags);

        notify->notify(notify, cpumask);

        free_cpumask_var(cpumask);
out:
        kref_put(&notify->kref, notify->release);
}

/**
 *      irq_set_affinity_notifier - control notification of IRQ affinity changes
 *      @irq:           Interrupt for which to enable/disable notification
 *      @notify:        Context for notification, or %NULL to disable
 *                      notification.  Function pointers must be initialised;
 *                      the other fields will be initialised by this function.
 *
 *      Must be called in process context.  Notification may only be enabled
 *      after the IRQ is allocated and must be disabled before the IRQ is
 *      freed using free_irq().
 */
int
irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify)
{
        struct irq_desc *desc = irq_to_desc(irq);
        struct irq_affinity_notify *old_notify;
        unsigned long flags;

        /* The release function is promised process context */
        might_sleep();

        if (!desc)
                return -EINVAL;

        /* Complete initialisation of *notify */
        if (notify) {
                notify->irq = irq;
                kref_init(&notify->kref);
                INIT_WORK(&notify->work, irq_affinity_notify);
        }

        raw_spin_lock_irqsave(&desc->lock, flags);
        old_notify = desc->affinity_notify;
        desc->affinity_notify = notify;
        raw_spin_unlock_irqrestore(&desc->lock, flags);

        if (old_notify)
                kref_put(&old_notify->kref, old_notify->release);

        return 0;
}
EXPORT_SYMBOL_GPL(irq_set_affinity_notifier);

#ifndef CONFIG_AUTO_IRQ_AFFINITY
/*
 * Generic version of the affinity autoselector.
 */
static int
setup_affinity(unsigned int irq, struct irq_desc *desc, struct cpumask *mask)
{
        struct irq_chip *chip = irq_desc_get_chip(desc);
        struct cpumask *set = irq_default_affinity;
        int ret;

        /* Excludes PER_CPU and NO_BALANCE interrupts */
        if (!irq_can_set_affinity(irq))
                return 0;

        /*
         * Preserve an userspace affinity setup, but make sure that
         * one of the targets is online.
         */
        if (irqd_has_set(&desc->irq_data, IRQD_AFFINITY_SET)) {
                if (cpumask_intersects(desc->irq_data.affinity,
                                       cpu_online_mask))
                        set = desc->irq_data.affinity;
                else {
                        irq_compat_clr_affinity(desc);
                        irqd_clear(&desc->irq_data, IRQD_AFFINITY_SET);
                }
        }

        cpumask_and(mask, cpu_online_mask, set);
        ret = chip->irq_set_affinity(&desc->irq_data, mask, false);
        switch (ret) {
        case IRQ_SET_MASK_OK:
                cpumask_copy(desc->irq_data.affinity, mask);
        case IRQ_SET_MASK_OK_NOCOPY:
                irq_set_thread_affinity(desc);
        }
        return 0;
}
#else
static inline int
setup_affinity(unsigned int irq, struct irq_desc *d, struct cpumask *mask)
{
        return irq_select_affinity(irq);
}
#endif

/*
 * Called when affinity is set via /proc/irq
 */
int irq_select_affinity_usr(unsigned int irq, struct cpumask *mask)
{
        struct irq_desc *desc = irq_to_desc(irq);
        unsigned long flags;
        int ret;

        raw_spin_lock_irqsave(&desc->lock, flags);
        ret = setup_affinity(irq, desc, mask);
        raw_spin_unlock_irqrestore(&desc->lock, flags);
        return ret;
}

#else
static inline int
setup_affinity(unsigned int irq, struct irq_desc *desc, struct cpumask *mask)
{
        return 0;
}
#endif

void __disable_irq(struct irq_desc *desc, unsigned int irq, bool suspend)
{
        if (suspend) {
                if (!desc->action || (desc->action->flags & IRQF_NO_SUSPEND))
                        return;
                desc->istate |= IRQS_SUSPENDED;
        }

        if (!desc->depth++)
                irq_disable(desc);
}

static int __disable_irq_nosync(unsigned int irq)
{
        unsigned long flags;
        struct irq_desc *desc = irq_get_desc_buslock(irq, &flags);

        if (!desc)
                return -EINVAL;
        __disable_irq(desc, irq, false);
        irq_put_desc_busunlock(desc, flags);
        return 0;
}

/**
 *      disable_irq_nosync - disable an irq without waiting
 *      @irq: Interrupt to disable
 *
 *      Disable the selected interrupt line.  Disables and Enables are
 *      nested.
 *      Unlike disable_irq(), this function does not ensure existing
 *      instances of the IRQ handler have completed before returning.
 *
 *      This function may be called from IRQ context.
 */
void disable_irq_nosync(unsigned int irq)
{
        __disable_irq_nosync(irq);
}
EXPORT_SYMBOL(disable_irq_nosync);

/**
 *      disable_irq - disable an irq and wait for completion
 *      @irq: Interrupt to disable
 *
 *      Disable the selected interrupt line.  Enables and Disables are
 *      nested.
 *      This function waits for any pending IRQ handlers for this interrupt
 *      to complete before returning. If you use this function while
 *      holding a resource the IRQ handler may need you will deadlock.
 *
 *      This function may be called - with care - from IRQ context.
 */
void disable_irq(unsigned int irq)
{
        if (!__disable_irq_nosync(irq))
                synchronize_irq(irq);
}
EXPORT_SYMBOL(disable_irq);

void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume)
{
        if (resume) {
                if (!(desc->istate & IRQS_SUSPENDED)) {
                        if (!desc->action)
                                return;
                        if (!(desc->action->flags & IRQF_FORCE_RESUME))
                                return;
                        /* Pretend that it got disabled ! */
                        desc->depth++;
                }
                desc->istate &= ~IRQS_SUSPENDED;
        }

        switch (desc->depth) {
        case 0:
 err_out:
                WARN(1, KERN_WARNING "Unbalanced enable for IRQ %d\n", irq);
                break;
        case 1: {
                if (desc->istate & IRQS_SUSPENDED)
                        goto err_out;
                /* Prevent probing on this irq: */
                irq_settings_set_noprobe(desc);
                irq_enable(desc);
                check_irq_resend(desc, irq);
                /* fall-through */
        }
        default:
                desc->depth--;
        }
}

/**
 *      enable_irq - enable handling of an irq
 *      @irq: Interrupt to enable
 *
 *      Undoes the effect of one call to disable_irq().  If this
 *      matches the last disable, processing of interrupts on this
 *      IRQ line is re-enabled.
 *
 *      This function may be called from IRQ context only when
 *      desc->irq_data.chip->bus_lock and desc->chip->bus_sync_unlock are NULL !
 */
void enable_irq(unsigned int irq)
{
        unsigned long flags;
        struct irq_desc *desc = irq_get_desc_buslock(irq, &flags);

        if (!desc)
                return;
        if (WARN(!desc->irq_data.chip,
                 KERN_ERR "enable_irq before setup/request_irq: irq %u\n", irq))
                goto out;

        __enable_irq(desc, irq, false);
out:
        irq_put_desc_busunlock(desc, flags);
}
EXPORT_SYMBOL(enable_irq);

static int set_irq_wake_real(unsigned int irq, unsigned int on)
{
        struct irq_desc *desc = irq_to_desc(irq);
        int ret = -ENXIO;

        if (desc->irq_data.chip->irq_set_wake)
                ret = desc->irq_data.chip->irq_set_wake(&desc->irq_data, on);

        return ret;
}

/**
 *      irq_set_irq_wake - control irq power management wakeup
 *      @irq:   interrupt to control
 *      @on:    enable/disable power management wakeup
 *
 *      Enable/disable power management wakeup mode, which is
 *      disabled by default.  Enables and disables must match,
 *      just as they match for non-wakeup mode support.
 *
 *      Wakeup mode lets this IRQ wake the system from sleep
 *      states like "suspend to RAM".
 */
int irq_set_irq_wake(unsigned int irq, unsigned int on)
{
        unsigned long flags;
        struct irq_desc *desc = irq_get_desc_buslock(irq, &flags);
        int ret = 0;

        /* wakeup-capable irqs can be shared between drivers that
         * don't need to have the same sleep mode behaviors.
         */
        if (on) {
                if (desc->wake_depth++ == 0) {
                        ret = set_irq_wake_real(irq, on);
                        if (ret)
                                desc->wake_depth = 0;
                        else
                                irqd_set(&desc->irq_data, IRQD_WAKEUP_STATE);
                }
        } else {
                if (desc->wake_depth == 0) {
                        WARN(1, "Unbalanced IRQ %d wake disable\n", irq);
                } else if (--desc->wake_depth == 0) {
                        ret = set_irq_wake_real(irq, on);
                        if (ret)
                                desc->wake_depth = 1;
                        else
                                irqd_clear(&desc->irq_data, IRQD_WAKEUP_STATE);
                }
        }
        irq_put_desc_busunlock(desc, flags);
        return ret;
}
EXPORT_SYMBOL(irq_set_irq_wake);

/*
 * Internal function that tells the architecture code whether a
 * particular irq has been exclusively allocated or is available
 * for driver use.
 */
int can_request_irq(unsigned int irq, unsigned long irqflags)
{
        unsigned long flags;
        struct irq_desc *desc = irq_get_desc_lock(irq, &flags);
        int canrequest = 0;

        if (!desc)
                return 0;

        if (irq_settings_can_request(desc)) {
                if (desc->action)
                        if (irqflags & desc->action->flags & IRQF_SHARED)
                                canrequest =1;
        }
        irq_put_desc_unlock(desc, flags);
        return canrequest;
}

int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
                      unsigned long flags)
{
        struct irq_chip *chip = desc->irq_data.chip;
        int ret, unmask = 0;

        if (!chip || !chip->irq_set_type) {
                /*
                 * IRQF_TRIGGER_* but the PIC does not support multiple
                 * flow-types?
                 */
                pr_debug("No set_type function for IRQ %d (%s)\n", irq,
                                chip ? (chip->name ? : "unknown") : "unknown");
                return 0;
        }

        flags &= IRQ_TYPE_SENSE_MASK;

        if (chip->flags & IRQCHIP_SET_TYPE_MASKED) {
                if (!(desc->istate & IRQS_MASKED))
                        mask_irq(desc);
                if (!(desc->istate & IRQS_DISABLED))
                        unmask = 1;
        }

        /* caller masked out all except trigger mode flags */
        ret = chip->irq_set_type(&desc->irq_data, flags);

        switch (ret) {
        case IRQ_SET_MASK_OK:
                irqd_clear(&desc->irq_data, IRQD_TRIGGER_MASK);
                irqd_set(&desc->irq_data, flags);

        case IRQ_SET_MASK_OK_NOCOPY:
                flags = irqd_get_trigger_type(&desc->irq_data);
                irq_settings_set_trigger_mask(desc, flags);
                irqd_clear(&desc->irq_data, IRQD_LEVEL);
                irq_settings_clr_level(desc);
                if (flags & IRQ_TYPE_LEVEL_MASK) {
                        irq_settings_set_level(desc);
                        irqd_set(&desc->irq_data, IRQD_LEVEL);
                }

                if (chip != desc->irq_data.chip)
                        irq_chip_set_defaults(desc->irq_data.chip);
                ret = 0;
                break;
        default:
                pr_err("setting trigger mode %lu for irq %u failed (%pF)\n",
                       flags, irq, chip->irq_set_type);
        }
        if (unmask)
                unmask_irq(desc);
        return ret;
}

/*
 * Default primary interrupt handler for threaded interrupts. Is
 * assigned as primary handler when request_threaded_irq is called
 * with handler == NULL. Useful for oneshot interrupts.
 */
static irqreturn_t irq_default_primary_handler(int irq, void *dev_id)
{
        return IRQ_WAKE_THREAD;
}

/*
 * Primary handler for nested threaded interrupts. Should never be
 * called.
 */
static irqreturn_t irq_nested_primary_handler(int irq, void *dev_id)
{
        WARN(1, "Primary handler called for nested irq %d\n", irq);
        return IRQ_NONE;
}

static int irq_wait_for_interrupt(struct irqaction *action)
{
        while (!kthread_should_stop()) {
                set_current_state(TASK_INTERRUPTIBLE);

                if (test_and_clear_bit(IRQTF_RUNTHREAD,
                                       &action->thread_flags)) {
                        __set_current_state(TASK_RUNNING);
                        return 0;
                }
                schedule();
        }
        return -1;
}

/*
 * Oneshot interrupts keep the irq line masked until the threaded
 * handler finished. unmask if the interrupt has not been disabled and
 * is marked MASKED.
 */
static void irq_finalize_oneshot(struct irq_desc *desc,
                                 struct irqaction *action, bool force)
{
        if (!(desc->istate & IRQS_ONESHOT))
                return;
again:
        chip_bus_lock(desc);
        raw_spin_lock_irq(&desc->lock);

        /*
         * Implausible though it may be we need to protect us against
         * the following scenario:
         *
         * The thread is faster done than the hard interrupt handler
         * on the other CPU. If we unmask the irq line then the
         * interrupt can come in again and masks the line, leaves due
         * to IRQS_INPROGRESS and the irq line is masked forever.
         *
         * This also serializes the state of shared oneshot handlers
         * versus "desc->threads_onehsot |= action->thread_mask;" in
         * irq_wake_thread(). See the comment there which explains the
         * serialization.
         */
        if (unlikely(desc->istate & IRQS_INPROGRESS)) {
                raw_spin_unlock_irq(&desc->lock);
                chip_bus_sync_unlock(desc);
                cpu_relax();
                goto again;
        }

        /*
         * Now check again, whether the thread should run. Otherwise
         * we would clear the threads_oneshot bit of this thread which
         * was just set.
         */
        if (!force && test_bit(IRQTF_RUNTHREAD, &action->thread_flags))
                goto out_unlock;

        desc->threads_oneshot &= ~action->thread_mask;

        if (!desc->threads_oneshot && !(desc->istate & IRQS_DISABLED) &&
            (desc->istate & IRQS_MASKED)) {
                irq_compat_clr_masked(desc);
                desc->istate &= ~IRQS_MASKED;
                desc->irq_data.chip->irq_unmask(&desc->irq_data);
        }
out_unlock:
        raw_spin_unlock_irq(&desc->lock);
        chip_bus_sync_unlock(desc);
}

#ifdef CONFIG_SMP
/*
 * Check whether we need to chasnge the affinity of the interrupt thread.
 */
static void
irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action)
{
        cpumask_var_t mask;

        if (!test_and_clear_bit(IRQTF_AFFINITY, &action->thread_flags))
                return;

        /*
         * In case we are out of memory we set IRQTF_AFFINITY again and
         * try again next time
         */
        if (!alloc_cpumask_var(&mask, GFP_KERNEL)) {
                set_bit(IRQTF_AFFINITY, &action->thread_flags);
                return;
        }

        raw_spin_lock_irq(&desc->lock);
        cpumask_copy(mask, desc->irq_data.affinity);
        raw_spin_unlock_irq(&desc->lock);

        set_cpus_allowed_ptr(current, mask);
        free_cpumask_var(mask);
}
#else
static inline void
irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action) { }
#endif

/*
 * Interrupts which are not explicitely requested as threaded
 * interrupts rely on the implicit bh/preempt disable of the hard irq
 * context. So we need to disable bh here to avoid deadlocks and other
 * side effects.
 */
static void
irq_forced_thread_fn(struct irq_desc *desc, struct irqaction *action)
{
        local_bh_disable();
        action->thread_fn(action->irq, action->dev_id);
        irq_finalize_oneshot(desc, action, false);
        local_bh_enable();
}

/*
 * Interrupts explicitely requested as threaded interupts want to be
 * preemtible - many of them need to sleep and wait for slow busses to
 * complete.
 */
static void irq_thread_fn(struct irq_desc *desc, struct irqaction *action)
{
        action->thread_fn(action->irq, action->dev_id);
        irq_finalize_oneshot(desc, action, false);
}

/*
 * Interrupt handler thread
 */
static int irq_thread(void *data)
{
        static const struct sched_param param = {
                .sched_priority = MAX_USER_RT_PRIO/2,
        };
        struct irqaction *action = data;
        struct irq_desc *desc = irq_to_desc(action->irq);
        void (*handler_fn)(struct irq_desc *desc, struct irqaction *action);
        int wake;

        if (force_irqthreads & test_bit(IRQTF_FORCED_THREAD,
                                        &action->thread_flags))
                handler_fn = irq_forced_thread_fn;
        else
                handler_fn = irq_thread_fn;

        sched_setscheduler(current, SCHED_FIFO, &param);
        current->irqaction = action;

        while (!irq_wait_for_interrupt(action)) {

                irq_thread_check_affinity(desc, action);

                atomic_inc(&desc->threads_active);

                raw_spin_lock_irq(&desc->lock);
                if (unlikely(desc->istate & IRQS_DISABLED)) {
                        /*
                         * CHECKME: We might need a dedicated
                         * IRQ_THREAD_PENDING flag here, which
                         * retriggers the thread in check_irq_resend()
                         * but AFAICT IRQS_PENDING should be fine as it
                         * retriggers the interrupt itself --- tglx
                         */
                        irq_compat_set_pending(desc);
                        desc->istate |= IRQS_PENDING;
                        raw_spin_unlock_irq(&desc->lock);
                } else {
                        raw_spin_unlock_irq(&desc->lock);
                        handler_fn(desc, action);
                }

                wake = atomic_dec_and_test(&desc->threads_active);

                if (wake && waitqueue_active(&desc->wait_for_threads))
                        wake_up(&desc->wait_for_threads);
        }

        /* Prevent a stale desc->threads_oneshot */
        irq_finalize_oneshot(desc, action, true);

        /*
         * Clear irqaction. Otherwise exit_irq_thread() would make
         * fuzz about an active irq thread going into nirvana.
         */
        current->irqaction = NULL;
        return 0;
}

/*
 * Called from do_exit()
 */
void exit_irq_thread(void)
{
        struct task_struct *tsk = current;
        struct irq_desc *desc;

        if (!tsk->irqaction)
                return;

        printk(KERN_ERR
               "exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n",
               tsk->comm ? tsk->comm : "", tsk->pid, tsk->irqaction->irq);

        desc = irq_to_desc(tsk->irqaction->irq);

        /*
         * Prevent a stale desc->threads_oneshot. Must be called
         * before setting the IRQTF_DIED flag.
         */
        irq_finalize_oneshot(desc, tsk->irqaction, true);

        /*
         * Set the THREAD DIED flag to prevent further wakeups of the
         * soon to be gone threaded handler.
         */
        set_bit(IRQTF_DIED, &tsk->irqaction->flags);
}

static void irq_setup_forced_threading(struct irqaction *new)
{
        if (!force_irqthreads)
                return;
        if (new->flags & (IRQF_NO_THREAD | IRQF_PERCPU | IRQF_ONESHOT))
                return;

        new->flags |= IRQF_ONESHOT;

        if (!new->thread_fn) {
                set_bit(IRQTF_FORCED_THREAD, &new->thread_flags);
                new->thread_fn = new->handler;
                new->handler = irq_default_primary_handler;
        }
}

/*
 * Internal function to register an irqaction - typically used to
 * allocate special interrupts that are part of the architecture.
 */
static int
__setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
{
        struct irqaction *old, **old_ptr;
        const char *old_name = NULL;
        unsigned long flags, thread_mask = 0;
        int ret, nested, shared = 0;
        cpumask_var_t mask;

        if (!desc)
                return -EINVAL;

        if (desc->irq_data.chip == &no_irq_chip)
                return -ENOSYS;
        /*
         * Some drivers like serial.c use request_irq() heavily,
         * so we have to be careful not to interfere with a
         * running system.
         */
        if (new->flags & IRQF_SAMPLE_RANDOM) {
                /*
                 * This function might sleep, we want to call it first,
                 * outside of the atomic block.
                 * Yes, this might clear the entropy pool if the wrong
                 * driver is attempted to be loaded, without actually
                 * installing a new handler, but is this really a problem,
                 * only the sysadmin is able to do this.
                 */
                rand_initialize_irq(irq);
        }

        /*
         * Check whether the interrupt nests into another interrupt
         * thread.
         */
        nested = irq_settings_is_nested_thread(desc);
        if (nested) {
                if (!new->thread_fn)
                        return -EINVAL;
                /*
                 * Replace the primary handler which was provided from
                 * the driver for non nested interrupt handling by the
                 * dummy function which warns when called.
                 */
                new->handler = irq_nested_primary_handler;
        } else {
                irq_setup_forced_threading(new);
        }

        /*
         * Create a handler thread when a thread function is supplied
         * and the interrupt does not nest into another interrupt
         * thread.
         */
        if (new->thread_fn && !nested) {
                struct task_struct *t;

                t = kthread_create(irq_thread, new, "irq/%d-%s", irq,
                                   new->name);
                if (IS_ERR(t))
                        return PTR_ERR(t);
                /*
                 * We keep the reference to the task struct even if
                 * the thread dies to avoid that the interrupt code
                 * references an already freed task_struct.
                 */
                get_task_struct(t);
                new->thread = t;
        }

        if (!alloc_cpumask_var(&mask, GFP_KERNEL)) {
                ret = -ENOMEM;
                goto out_thread;
        }

        /*
         * The following block of code has to be executed atomically
         */
        raw_spin_lock_irqsave(&desc->lock, flags);
        old_ptr = &desc->action;
        old = *old_ptr;
        if (old) {
                /*
                 * Can't share interrupts unless both agree to and are
                 * the same type (level, edge, polarity). So both flag
                 * fields must have IRQF_SHARED set and the bits which
                 * set the trigger type must match. Also all must
                 * agree on ONESHOT.
                 */
                if (!((old->flags & new->flags) & IRQF_SHARED) ||
                    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK) ||
                    ((old->flags ^ new->flags) & IRQF_ONESHOT)) {
                        old_name = old->name;
                        goto mismatch;
                }

                /* All handlers must agree on per-cpuness */
                if ((old->flags & IRQF_PERCPU) !=
                    (new->flags & IRQF_PERCPU))
                        goto mismatch;

                /* add new interrupt at end of irq queue */
                do {
                        thread_mask |= old->thread_mask;
                        old_ptr = &old->next;
                        old = *old_ptr;
                } while (old);
                shared = 1;
        }

        /*
         * Setup the thread mask for this irqaction. Unlikely to have
         * 32 resp 64 irqs sharing one line, but who knows.
         */
        if (new->flags & IRQF_ONESHOT && thread_mask == ~0UL) {
                ret = -EBUSY;
                goto out_mask;
        }
        new->thread_mask = 1 << ffz(thread_mask);

        if (!shared) {
                irq_chip_set_defaults(desc->irq_data.chip);

                init_waitqueue_head(&desc->wait_for_threads);

                /* Setup the type (level, edge polarity) if configured: */
                if (new->flags & IRQF_TRIGGER_MASK) {
                        ret = __irq_set_trigger(desc, irq,
                                        new->flags & IRQF_TRIGGER_MASK);

                        if (ret)
                                goto out_mask;
                }

                desc->istate &= ~(IRQS_AUTODETECT | IRQS_SPURIOUS_DISABLED | \
                                  IRQS_INPROGRESS | IRQS_ONESHOT | \
                                  IRQS_WAITING);

                if (new->flags & IRQF_PERCPU) {
                        irqd_set(&desc->irq_data, IRQD_PER_CPU);
                        irq_settings_set_per_cpu(desc);
                }

                if (new->flags & IRQF_ONESHOT)
                        desc->istate |= IRQS_ONESHOT;

                if (irq_settings_can_autoenable(desc))
                        irq_startup(desc);
                else
                        /* Undo nested disables: */
                        desc->depth = 1;

                /* Exclude IRQ from balancing if requested */
                if (new->flags & IRQF_NOBALANCING) {
                        irq_settings_set_no_balancing(desc);
                        irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
                }

                /* Set default affinity mask once everything is setup */
                setup_affinity(irq, desc, mask);

        } else if (new->flags & IRQF_TRIGGER_MASK) {
                unsigned int nmsk = new->flags & IRQF_TRIGGER_MASK;
                unsigned int omsk = irq_settings_get_trigger_mask(desc);

                if (nmsk != omsk)
                        /* hope the handler works with current  trigger mode */
                        pr_warning("IRQ %d uses trigger mode %u; requested %u\n",
                                   irq, nmsk, omsk);
        }

        new->irq = irq;
        *old_ptr = new;

        /* Reset broken irq detection when installing new handler */
        desc->irq_count = 0;
        desc->irqs_unhandled = 0;

        /*
         * Check whether we disabled the irq via the spurious handler
         * before. Reenable it and give it another chance.
         */
        if (shared && (desc->istate & IRQS_SPURIOUS_DISABLED)) {
                desc->istate &= ~IRQS_SPURIOUS_DISABLED;
                __enable_irq(desc, irq, false);
        }

        raw_spin_unlock_irqrestore(&desc->lock, flags);

        /*
         * Strictly no need to wake it up, but hung_task complains
         * when no hard interrupt wakes the thread up.
         */
        if (new->thread)
                wake_up_process(new->thread);

        register_irq_proc(irq, desc);
        new->dir = NULL;
        register_handler_proc(irq, new);

        return 0;

mismatch:
#ifdef CONFIG_DEBUG_SHIRQ
        if (!(new->flags & IRQF_PROBE_SHARED)) {
                printk(KERN_ERR "IRQ handler type mismatch for IRQ %d\n", irq);
                if (old_name)
                        printk(KERN_ERR "current handler: %s\n", old_name);
                dump_stack();
        }
#endif
        ret = -EBUSY;

out_mask:
        raw_spin_unlock_irqrestore(&desc->lock, flags);
        free_cpumask_var(mask);

out_thread:
        if (new->thread) {
                struct task_struct *t = new->thread;

                new->thread = NULL;
                if (likely(!test_bit(IRQTF_DIED, &new->thread_flags)))
                        kthread_stop(t);
                put_task_struct(t);
        }
        return ret;
}

/**
 *      setup_irq - setup an interrupt
 *      @irq: Interrupt line to setup
 *      @act: irqaction for the interrupt
 *
 * Used to statically setup interrupts in the early boot process.
 */
int setup_irq(unsigned int irq, struct irqaction *act)
{
        int retval;
        struct irq_desc *desc = irq_to_desc(irq);

        chip_bus_lock(desc);
        retval = __setup_irq(irq, desc, act);
        chip_bus_sync_unlock(desc);

        return retval;
}
EXPORT_SYMBOL_GPL(setup_irq);

 /*
 * Internal function to unregister an irqaction - used to free
 * regular and special interrupts that are part of the architecture.
 */
static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
{
        struct irq_desc *desc = irq_to_desc(irq);
        struct irqaction *action, **action_ptr;
        unsigned long flags;

        WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!\n", irq);

        if (!desc)
                return NULL;

        raw_spin_lock_irqsave(&desc->lock, flags);

        /*
         * There can be multiple actions per IRQ descriptor, find the right
         * one based on the dev_id:
         */
        action_ptr = &desc->action;
        for (;;) {
                action = *action_ptr;

                if (!action) {
                        WARN(1, "Trying to free already-free IRQ %d\n", irq);
                        raw_spin_unlock_irqrestore(&desc->lock, flags);

                        return NULL;
                }

                if (action->dev_id == dev_id)
                        break;
                action_ptr = &action->next;
        }

        /* Found it - now remove it from the list of entries: */
        *action_ptr = action->next;

        /* Currently used only by UML, might disappear one day: */
#ifdef CONFIG_IRQ_RELEASE_METHOD
        if (desc->irq_data.chip->release)
                desc->irq_data.chip->release(irq, dev_id);
#endif

        /* If this was the last handler, shut down the IRQ line: */
        if (!desc->action)
                irq_shutdown(desc);

#ifdef CONFIG_SMP
        /* make sure affinity_hint is cleaned up */
        if (WARN_ON_ONCE(desc->affinity_hint))
                desc->affinity_hint = NULL;
#endif

        raw_spin_unlock_irqrestore(&desc->lock, flags);

        unregister_handler_proc(irq, action);

        /* Make sure it's not being used on another CPU: */
        synchronize_irq(irq);

#ifdef CONFIG_DEBUG_SHIRQ
        /*
         * It's a shared IRQ -- the driver ought to be prepared for an IRQ
         * event to happen even now it's being freed, so let's make sure that
         * is so by doing an extra call to the handler ....
         *
         * ( We do this after actually deregistering it, to make sure that a
         *   'real' IRQ doesn't run in * parallel with our fake. )
         */
        if (action->flags & IRQF_SHARED) {
                local_irq_save(flags);
                action->handler(irq, dev_id);
                local_irq_restore(flags);
        }
#endif

        if (action->thread) {
                if (!test_bit(IRQTF_DIED, &action->thread_flags))
                        kthread_stop(action->thread);
                put_task_struct(action->thread);
        }

        return action;
}

/**
 *      remove_irq - free an interrupt
 *      @irq: Interrupt line to free
 *      @act: irqaction for the interrupt
 *
 * Used to remove interrupts statically setup by the early boot process.
 */
void remove_irq(unsigned int irq, struct irqaction *act)
{
        __free_irq(irq, act->dev_id);
}
EXPORT_SYMBOL_GPL(remove_irq);

/**
 *      free_irq - free an interrupt allocated with request_irq
 *      @irq: Interrupt line to free
 *      @dev_id: Device identity to free
 *
 *      Remove an interrupt handler. The handler is removed and if the
 *      interrupt line is no longer in use by any driver it is disabled.
 *      On a shared IRQ the caller must ensure the interrupt is disabled
 *      on the card it drives before calling this function. The function
 *      does not return until any executing interrupts for this IRQ
 *      have completed.
 *
 *      This function must not be called from interrupt context.
 */
void free_irq(unsigned int irq, void *dev_id)
{
        struct irq_desc *desc = irq_to_desc(irq);

        if (!desc)
                return;

#ifdef CONFIG_SMP
        if (WARN_ON(desc->affinity_notify))
                desc->affinity_notify = NULL;
#endif

        chip_bus_lock(desc);
        kfree(__free_irq(irq, dev_id));
        chip_bus_sync_unlock(desc);
}
EXPORT_SYMBOL(free_irq);

/**
 *      request_threaded_irq - allocate an interrupt line
 *      @irq: Interrupt line to allocate
 *      @handler: Function to be called when the IRQ occurs.
 *                Primary handler for threaded interrupts
 *                If NULL and thread_fn != NULL the default
 *                primary handler is installed
 *      @thread_fn: Function called from the irq handler thread
 *                  If NULL, no irq thread is created
 *      @irqflags: Interrupt type flags
 *      @devname: An ascii name for the claiming device
 *      @dev_id: A cookie passed back to the handler function
 *
 *      This call allocates interrupt resources and enables the
 *      interrupt line and IRQ handling. From the point this
 *      call is made your handler function may be invoked. Since
 *      your handler function must clear any interrupt the board
 *      raises, you must take care both to initialise your hardware
 *      and to set up the interrupt handler in the right order.
 *
 *      If you want to set up a threaded irq handler for your device
 *      then you need to supply @handler and @thread_fn. @handler ist
 *      still called in hard interrupt context and has to check
 *      whether the interrupt originates from the device. If yes it
 *      needs to disable the interrupt on the device and return
 *      IRQ_WAKE_THREAD which will wake up the handler thread and run
 *      @thread_fn. This split handler design is necessary to support
 *      shared interrupts.
 *
 *      Dev_id must be globally unique. Normally the address of the
 *      device data structure is used as the cookie. Since the handler
 *      receives this value it makes sense to use it.
 *
 *      If your interrupt is shared you must pass a non NULL dev_id
 *      as this is required when freeing the interrupt.
 *
 *      Flags:
 *
 *      IRQF_SHARED             Interrupt is shared
 *      IRQF_SAMPLE_RANDOM      The interrupt can be used for entropy
 *      IRQF_TRIGGER_*          Specify active edge(s) or level
 *
 */
int request_threaded_irq(unsigned int irq, irq_handler_t handler,
                         irq_handler_t thread_fn, unsigned long irqflags,
                         const char *devname, void *dev_id)
{
        struct irqaction *action;
        struct irq_desc *desc;
        int retval;

        /*
         * Sanity-check: shared interrupts must pass in a real dev-ID,
         * otherwise we'll have trouble later trying to figure out
         * which interrupt is which (messes up the interrupt freeing
         * logic etc).
         */
        if ((irqflags & IRQF_SHARED) && !dev_id)
                return -EINVAL;

        desc = irq_to_desc(irq);
        if (!desc)
                return -EINVAL;

        if (!irq_settings_can_request(desc))
                return -EINVAL;

        if (!handler) {
                if (!thread_fn)
                        return -EINVAL;
                handler = irq_default_primary_handler;
        }

        action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
        if (!action)
                return -ENOMEM;

        action->handler = handler;
        action->thread_fn = thread_fn;
        action->flags = irqflags;
        action->name = devname;
        action->dev_id = dev_id;

        chip_bus_lock(desc);
        retval = __setup_irq(irq, desc, action);
        chip_bus_sync_unlock(desc);

        if (retval)
                kfree(action);

#ifdef CONFIG_DEBUG_SHIRQ_FIXME
        if (!retval && (irqflags & IRQF_SHARED)) {
                /*
                 * It's a shared IRQ -- the driver ought to be prepared for it
                 * to happen immediately, so let's make sure....
                 * We disable the irq to make sure that a 'real' IRQ doesn't
                 * run in parallel with our fake.
                 */
                unsigned long flags;

                disable_irq(irq);
                local_irq_save(flags);

                handler(irq, dev_id);

                local_irq_restore(flags);
                enable_irq(irq);
        }
#endif
        return retval;
}
EXPORT_SYMBOL(request_threaded_irq);

/**
 *      request_any_context_irq - allocate an interrupt line
 *      @irq: Interrupt line to allocate
 *      @handler: Function to be called when the IRQ occurs.
 *                Threaded handler for threaded interrupts.
 *      @flags: Interrupt type flags
 *      @name: An ascii name for the claiming device
 *      @dev_id: A cookie passed back to the handler function
 *
 *      This call allocates interrupt resources and enables the
 *      interrupt line and IRQ handling. It selects either a
 *      hardirq or threaded handling method depending on the
 *      context.
 *
 *      On failure, it returns a negative value. On success,
 *      it returns either IRQC_IS_HARDIRQ or IRQC_IS_NESTED.
 */
int request_any_context_irq(unsigned int irq, irq_handler_t handler,
                            unsigned long flags, const char *name, void *dev_id)
{
        struct irq_desc *desc = irq_to_desc(irq);
        int ret;

        if (!desc)
                return -EINVAL;

        if (irq_settings_is_nested_thread(desc)) {
                ret = request_threaded_irq(irq, NULL, handler,
                                           flags, name, dev_id);
                return !ret ? IRQC_IS_NESTED : ret;
        }

        ret = request_irq(irq, handler, flags, name, dev_id);
        return !ret ? IRQC_IS_HARDIRQ : ret;
}
EXPORT_SYMBOL_GPL(request_any_context_irq);